Battery lost capacity

J.B.

Pedelecer
May 23, 2016
55
7
Lincolnshire
I use my kalkhoff pro connect in the winter to transport my dog. I keep meaning to use it the rest of the year but I generally just use my other bikes. It went 7 months without use. The battery was charged and left on the bike. Needed for 24 mile round trip only just made the 12 miles there. Reckon there was 30 miles of power in it before storage. That's pulling a 14.5 kg trailer with a 18kg dog in it.
Bike shows a full charge when charged up. It drops to 9 bars from 10 stays there for a while and rapidly down to 1. It may miss out some bars not sure. I have run it to zero bars but it has yet to cut out.
Obviously would prefer not to buy a new battery. I am using it at the moment to fetch firewood etc with the trailer on just to see how far it will go. I expect about two trips locally before it reverts to one bar. Roughly 15miles. Bought second hand with I think 2,500miles on the clock and I have added 2,000. I don't use the motor all the time ie on the flat I switch it off.
Any ideas? I read that maybe I should run it till it cuts out then charge it up. So once it reaches one or zero without the trailer ride round till it cuts out? Odd how it always shows a full charge but clearly (going by the bars) isn't hold one.
Any help appreciated.
36volts 17ah battery
 

Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
322
55
72
I use my kalkhoff pro connect in the winter to transport my dog. I keep meaning to use it the rest of the year but I generally just use my other bikes. It went 7 months without use. The battery was charged and left on the bike. Needed for 24 mile round trip only just made the 12 miles there. Reckon there was 30 miles of power in it before storage. That's pulling a 14.5 kg trailer with a 18kg dog in it.
Bike shows a full charge when charged up. It drops to 9 bars from 10 stays there for a while and rapidly down to 1. It may miss out some bars not sure. I have run it to zero bars but it has yet to cut out.
Obviously would prefer not to buy a new battery. I am using it at the moment to fetch firewood etc with the trailer on just to see how far it will go. I expect about two trips locally before it reverts to one bar. Roughly 15miles. Bought second hand with I think 2,500miles on the clock and I have added 2,000. I don't use the motor all the time ie on the flat I switch it off.
Any ideas? I read that maybe I should run it till it cuts out then charge it up. So once it reaches one or zero without the trailer ride round till it cuts out? Odd how it always shows a full charge but clearly (going by the bars) isn't hold one.
Any help appreciated.
36volts 17ah battery
Batteries are like humans, they need to be exercised regularly.
Ride only this bike and if you are lucky, once maybe 10 charge/discharge cycles have been made, it should regain its capacity, but no guarantee.
Li-ion batteries are sensitive.
If they go below a certain level of voltage (36 v Less than 28 volts), they will not charge again, till you find and use what I call a 0 volt charger....not easy to find!
Stark sells one for $95!! But you don't need that at this time.
Also, once a battery is charged, remove it from the charger, as even tiny over charging reduces capacity. Even though the charger shows green,that just means the large charing current has reduced, not that the charger is OFF, as there is a tiny voltage still being applied!!
I hope this helps
Andy
 

J.B.

Pedelecer
May 23, 2016
55
7
Lincolnshire
Thank you.
What do you reckon to me doing a full discharge? Ride until motor cuts out then full recharge as soon as I get home.
 

flecc

Member
Oct 25, 2006
42,317
17,932
These Kalkhoff-BMZ batteries supposely have a sleep mode, meaning the BMS shuts down after a couple of weeks, preventing further discharge. This doesn't seem to have worked for you.

I'd recommend you fully charge, then ride it to cut-off before fully charging again. Do that again if necessary. The ride doesn't have to be continuous, spread over a day or three is ok.

Have you tried a capacity check? To do that, hold down the test button for at least 5 seconds and the number of bars that appear indicate the potential capacity of the battery, each bar being 20% of the nominal capacity.

After the above ride to empty, try the capacity test again before and after charging.
.
 
Last edited:

Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
322
55
72
Thank you.
What do you reckon to me doing a full discharge? Ride until motor cuts out then full recharge as soon as I get home.
Good move, or should I say good move"s", as you will need to do it quite often. Note the miles you achieve each time, that will hopefully slowly increase for each ride, and you can be near home when the battery is empty!
regards
Andy.
 

GLJoe

Esteemed Pedelecer
May 21, 2017
401
168
UK
Also, once a battery is charged, remove it from the charger, as even tiny over charging reduces capacity. Even though the charger shows green,that just means the large charing current has reduced, not that the charger is OFF, as there is a tiny voltage still being applied!!
Bear in mind that if the charging system needs some time to balance the cells at the top of the charge, then this might be totally incorrect advice.

Decent charging systems will NOT overcharge the batteries when the main charging is complete.
There is a strong possibility that the fault described might be some cells in the pack having discharged more than others, so the battery is no longer balanced. Doing a number of full discharge/charge cycles might eventually sort things out, so doing that is good advice. However unless one is 100% certain that you have a pretty useless charging system that absolutely must be disconnected after it shows a finished status, then its probably a good idea to also LEAVE the charger on and connected for a good few hours after 'finishing' in case it needs this time to help any balancing to occur.
 

Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
322
55
72
Bear in mind that if the charging system needs some time to balance the cells at the top of the charge, then this might be totally incorrect advice.

Decent charging systems will NOT overcharge the batteries when the main charging is complete.
There is a strong possibility that the fault described might be some cells in the pack having discharged more than others, so the battery is no longer balanced. Doing a number of full discharge/charge cycles might eventually sort things out, so doing that is good advice. However unless one is 100% certain that you have a pretty useless charging system that absolutely must be disconnected after it shows a finished status, then its probably a good idea to also LEAVE the charger on and connected for a good few hours after 'finishing' in case it needs this time to help any balancing to occur.
How can a person tell how "decent" a charging system is? Impossible and 100% guesswork!
Also. the balancing is carried out by the battery itself, shuffling around and evening out cell capacity. Removing the charger affects nothing once green is shown! The charger cannot "see" which cell has what capacity/charge!!
Read here:-
https://batteryuniversity.com/learn/article/bu_803a_cell_mismatch_balancing
A battery expert once said: “I have not seen a cell balancing circuit that works.” For multi-cell packs, he suggested using quality Li-ion cells that have been factory-sorted on capacity and voltage. This works well for Li-ion packs up to 24V; packs above 24V should have balancing. Most balancing is passive; active balancing is complex and is only used in very large systems.
I hope this helps.
Andy
 

anotherkiwi

Esteemed Pedelecer
Jan 26, 2015
7,595
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By leaving the charger on with a trickle of current for a while you ensure that the cells balance up to nominative voltage and do not balance down to the lowest cell group voltage. A charger is a "dumb" box that outputs 42v @ 2 Amps - the BMS signals if it will accept charge or not. It also sets charge rate at the end of charge.

So if a battery over charges it is a faulty BMS which is your problem.

I haven't balance charged my Graphene Lipo battery since new a couple of years ago. The cells are all within 0.01v of each other.
 
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J.B.

Pedelecer
May 23, 2016
55
7
Lincolnshire
Thought the capacity may have increased as half a mile from home still 7 bars showing. Looked again when I got home 1 bar showing. Final half mile downhill and more or less flat? Did another 3 miles before it went to zero but couldn't get it to completely cut out (hungry) Despite riding up down a hill with a trailer full of firewood. Just charged it again took about an hour?
 

J.B.

Pedelecer
May 23, 2016
55
7
Lincolnshire
These Kalkhoff-BMZ batteries supposely have a sleep mode, meaning the BMS shuts down after a couple of weeks, preventing further discharge. This doesn't seem to have worked for you.

I'd recommend you fully charge, then ride it to cut-off before fully charging again. Do that again if necessary. The ride doesn't have to be continuous, spread over a day or three is ok.

Have you tried a capacity check? To do that, hold down the test button for at least 5 seconds and the number of bars that appear indicate the potential capacity of the battery, each bar being 20% of the nominal capacity.

After the above ride to empty, try the capacity test again before and after charging.
.
Held button down for 5 seconds went to 2 lights. That's after it had been charged.
 

anotherkiwi

Esteemed Pedelecer
Jan 26, 2015
7,595
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Thought the capacity may have increased as half a mile from home still 7 bars showing. Looked again when I got home 1 bar showing. Final half mile downhill and more or less flat? Did another 3 miles before it went to zero but couldn't get it to completely cut out (hungry) Despite riding up down a hill with a trailer full of firewood. Just charged it again took about an hour?
17 ah? Takes a lot longer than an hour to charge a big battery like that.

Held button down for 5 seconds went to 2 lights. That's after it had been charged.
Something is wrong...
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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To know exactly what is occurring the battery requires opening to check the sense wire voltages, this will tell you if any parallel strings/groups are out of balance. If strings/groups are unbalanced then the low ones will hit lvc first or battery performance will panda to these lower cells.

If all read he same and are in balance then capacity has most likely decreased and cells are past their best. Even poor capacity cells will fully charge, the voltage just collapses quicker under load.
 
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flecc

Member
Oct 25, 2006
42,317
17,932
Held button down for 5 seconds went to 2 lights. That's after it had been charged.
That means you only have around 40% capacity left after too long in storage uncharged.

You can try the running to cut-off and then fully charging, doing this two or more times to see if there's any gain each time on the capacity test.
.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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17 ah? Takes a lot longer than an hour to charge a big battery like that.

Something is wrong...
As AK has alluded too, 17ah in good condition should take 8.5 - 9.5hrs to fully balance charge if drained to lvc with a 2a charger.
 

GLJoe

Esteemed Pedelecer
May 21, 2017
401
168
UK
How can a person tell how "decent" a charging system is? Impossible and 100% guesswork!
No, not impossible. As just one example, people often do teardowns of things such as battery packs, so a little bit of simple research can often let one find out what's been discovered, and even what circuitry/chips have been used in the design.


Also. the balancing is carried out by the battery itself, shuffling around and evening out cell capacity. Removing the charger affects nothing once green is shown! The charger cannot "see" which cell has what capacity/charge!!
The 'shuffling' you speak of is only one method of balancing, and from what I can gather, is not commonly implemented.
If the balancing is done by simple discharging of cell groups that have quickly reached their max voltage, then you could still have a design that needs the power supply to either provide a trickle charge, or even kick back in now and again during the balancing phase.


Read here:-
https://batteryuniversity.com/learn/article/bu_803a_cell_mismatch_balancing
A battery expert once said: “I have not seen a cell balancing circuit that works.” For multi-cell packs, he suggested using quality Li-ion cells that have been factory-sorted on capacity and voltage. This works well for Li-ion packs up to 24V; packs above 24V should have balancing. Most balancing is passive; active balancing is complex and is only used in very large systems.
I hope this helps.
A very vague quote, with no citation/reference source so of questionable validity right from the start! however it (and other text on the matter) seems to be suggesting that for lower voltage packs in things such as drills, they often don't bother with balancing, because if you initially use matched cells, the battery pack will generally last long enough to outlive the warranty period!

But also - "packs above 24v should have balancing'. There we are then. The majority of ebike battery packs are 36/48v ! so they need balancing !!
 

J.B.

Pedelecer
May 23, 2016
55
7
Lincolnshire
To know exactly what is occurring the battery requires opening to check the sense wire voltages, this will tell you if any parallel strings/groups are out of balance. If strings/groups are unbalanced then the low ones will hit lvc first or battery performance will panda to these lower cells.

If all read he same and are in balance then capacity has most likely decreased and cells are past their best. Even poor capacity cells will fully charge, the voltage just collapses quicker under load.
Well I certainly don't know what your on about!! Opening up batteries and? Although I might know a man who does....who I don't see very often. He built two pedelecs. I will stick with running them until they show no bars and hopefully get round to running to zero power. In the meantime I have a very tasty pile of wood and a well exercised dog!!
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
7,305
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Well I certainly don't know what your on about!! Opening up batteries and? Although I might know a man who does....who I don't see very often. He built two pedelecs. I will stick with running them until they show no bars and hopefully get round to running to zero power. In the meantime I have a very tasty pile of wood and a well exercised dog!!
:eek: Best not even think of opening it then.
Generally those with diy testing skill can take individual cell group voltage measurements, this can help determining why a battery may be under performing or failing.
 

DynatechFan

Pedelecer
Oct 20, 2017
212
68
t'North
bit if a newb question / comment but my understanding is the best way to build / rebuild capacity in a battery was to run it to 75% empty and recharge. Deep cycle discharging to empty is bad for batteries - no?